The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences.
Introduction
Ornithodoros turicata (Figure 1), commonly referred to as the relapsing fever tick, is a soft tick species belonging to the family Argasidae. It is a key vector of Borrelia turicatae, a spirochete bacterium responsible for causing tick-borne relapsing fever (TBRF). Known for its elusive behavior, O. turicata feeds rapidly and inhabits concealed environments such as caves, animal burrows, and cabins. While O. turicata is more commonly found in the southwestern United States, it has been reported in Florida, expanding its recognized range. This tick’s ability to survive for extended periods and to rapidly transmit pathogens during blood meals makes it a significant vector of zoonotic diseases and presents major challenges for public health management and disease prevention (Lopez et al. 2016).
Credit: Credits: A) U.S. Army Center for Health Promotion and Preventive Medicine, 16 May 201, used with permission; B) and C) Lorenza Beati, US National Tick Collection at George Southern University, used with permission
Synonymy
Ornithodoros turicata has been reclassified numerous times since its initial description. The species was originally described by Antoine Louis Dugès in 1876 under the genus Ornithodoros. It was later reclassified as Alectorobius turicata by Cooley and Kohls in 1944 during their extensive review of Argasidae. Neumann introduced the synonym Ornithodoros dugesi in 1908, which was subsequently invalidated and subsumed under O. turicata. Hoogstraal, in his foundational work on tick taxonomy in 1985, placed the species within the subgenus Ornithodoros. Beck et al. (1986) revived the subspecies classification of Ornithodoros turicata, distinguishing O. turicata americanus—found in Florida—from O. turicata turicata, which inhabits the arid regions of the southwestern United States, based on observed ecological and biological differences in life cycle characteristics, host associations, and microhabitat preferences.
Distribution
The two subspecies of O. turicata currently recognized, exhibiting disjunct geographic ranges with Ornithodoros turicata turicata, present throughout the southwestern United States (including Texas, New Mexico and Arizona), and Ornithodoros turicata americanus, which occurs in parts of Florida (Donaldson et al. 2016; Figure 4A).
Ornithodoros turicata turicata thrives in arid and semi-arid climates and is commonly found in dark, climatically stable microhabitats, such as the wildlife burrows of rodents and reptiles, as well as natural rock crevices and bat roosts (Donaldson et al. 2016). In Florida, O. turicata americanus populations have only been recovered from gopher tortoise (Gopherus polyphemus) burrows, which may serve as the tick’s primary microhabitat in locations with a more humid climate (Adeyeye & Butler, 1989; Donaldson et al. 2016; Canino et al. 2024). In a statewide survey of Florida, Botero-Cañola et al. (2024) were able to confirm the presence of these soft ticks in 33 counties across the state. This study also utilized Integrated Species Distribution Models (ISDM) to predict the distribution of O. turicata americanus, identifying that 62% of Florida comprises suitable habitat for this tick subspecies (Figure 4B). Its presence in the state underscores the need for increased awareness of its ecology and potential to spread diseases like TBRF (Dworkin et al. 2008).
Credit: A) prediction model developed by Donaldson et al. (2016), used with permission; and B) Suitable habitat map developed by Botero-Cañola et al. (2024), used with permission
Description
Ornithodoros turicata like all soft ticks is characterized by the absence of a scutum (hard outer plate) and mouthparts that are not visible from above.
Adults
Adults are small in size measuring approximately 4 to 10 mm (3/16 to 1/3 in) in length, are more robust and equipped with functional reproductive organs. They have a rounded body shape, and a wrinkled, leathery texture (Hoogstraal 1985). Their coloration is generally brown or grayish-brown, which helps them blend into their natural environment. Within the genus Ornithodoros, O. turicata can be identified from other species by its relatively large size, broadly oval shape, and distinct cuticular ornamentation, including granular sculpturing on the dorsal surface (Cooley and Kohls 1944). Morphological differences, such as the arrangement and size of dorsal setae and the characteristics of the dentition of the specialized feeding mouthparts, known as the hypostome, help distinguish O. turicata from closely related species like Ornithodoros parkeri and Ornithodoros coriaceus (Cooley and Kohls 1944; Hoogstraal 1985). The hypostome dentition consists of 3–4 rows of small, sharp, recurved teeth on either side, which enables a secure attachment during feeding and serves as a key diagnostic feature for species identification (Figure 2).
Eggs
After mating with a male, female O. turicata can lay eggs in batch of ~100 eggs. Female will lay batches of eggs multiple time throughout their lifespan.
Larvae
Six-legged larvae that typically measuring about 0.5 to 1.0 mm (~1/32 in) in length hatch from the eggs (Hoogstraal 1985).
Credit: Subset of images from Muñoz-Leal et al. 2019, used with permission
Nymphs
Nymphs, are larger and range from 1.5 to 3.0 mm (~1/16 to 1/8 in) depending on the instar, lack the reproductive structures seen in adults and are generally less sclerotized
Life Cycle and/or Biology
The life cycle of O. turicata includes four stages: egg, larva, nymph, and adult (Figure 3). After hatching from the egg, the larvae feed before molting into eight-legged nymph, which can undergo four to six instars before reaching adulthood (Donaldson et al. 2016). Ornithodoros turicata feeding behavior is typical of the one of soft ticks and characterized by rapid attachment and feeding, facilitated by their specialized hypostome and anticoagulant secretions. The rapidity of the bloodmeal minimizes the tick’s chances of being detected by the host. As an example, Ornithodoros turicata americanus nymphs and adults typically completing a blood meal in less than an hour—often within just 15 to 30 minutes—highlighting the species’ efficiency and stealth as a vector (Beck 1986). Larvae, nymphs and adults often taking multiple meals throughout their lifespan. A remarkable feature of O. turicata is its ability to survive for years without feeding. This adaptation allows it to endure long periods of host absence, emerging opportunistically when a potential host enters its habitat (Donaldson et al. 2016). Its cryptic lifestyle means it resides in dark, sheltered environments, such as burrows, caves, or beneath loose soil and rocks, avoiding detection. DNA and stable isotope based bloodmeal analyses revealed that O. turicata feeds on a wide range of vertebrate hosts, including mammals such as livestock (cattle and pigs), companion animals (dogs), and humans, as well as reptiles, amphibians, and birds. This emphasizes its ecological versatility and potential for spillover of pathogens from wildlife to humans (Kleinerman et al. 2021; Busselman et al. 2021; Kim et al. 2021; Balasubramanian et al. 2024).
Credit: Moriah Garrison, UF/IFAS; created with Canva
Medical Importance
Ornithodoros turicata is a significant vector of B. turicatae, one of the causative agents of TBRF. Transmission of TBRF occurs when an infected O. turicata feeds on a human host, injecting the spirochete through its saliva within moments of feeding (Bourret et al., 2019). The ecology of B. turicatae remains relatively understudied but the primary reservoirs of borrelia species are rodents. In Texas, B. turicatae was commonly found infecting both domestic and wild canine including dogs, grey foxes and coyotes (Krishnavajhala et al. 2021). Krishnavajhala et al. (2021) also demonstrated that geographical populations of O. turicata exhibit variations in their vector competence for Borrelia turicatae, which could influence the epidemiology of TBRF across regions. Evidence of transovarial transmission of B. turicatae from infected O. turicata to their offspring is known to occur showing the role of O.turicata as reservoir of the virus in nature (Filatov et al. 2023; Francis 1938).
Vector competence assays in controlled laboratory settings show the ability O. turicata to transmit African swine fever virus (ASFV) to swine hosts (Hess et al. 1987). Although ASFV is not present in the United States currently, its introduction could devastate domestic and feral swine populations, with Ornithodoros ticks serving as a means for virus persistence in the environment (Golnar et al. 2019, Wormington et al. 2019). African swine fever virus introduction could lead to severe economic losses and necessitate strict biosecurity measures to control its spread (Brown and Bevins 2018).
Ornithodoros turicata’s ability to feed quickly and in secluded habitats means that exposures to this tick species may go unnoticed. Public health strategies should focus on educating individuals about avoiding high-risk areas, such as caves or cabins and be vigilant while conducting activities near wildlife burrows. The use of protective measures like tick repellents and proper clothing (e.g.: long pants, long sleeve shirts, tucking pants into socks) can help reduce tick-host contact. More research into the ecology of these soft ticks, the transmission dynamics of the pathogens they carry, and the risk of disease spread to humans and livestock is essential to better understanding this disease vector.
Selected References
Adeyeye OA, Butler JF. (1989). Population structure and seasonal intra-burrow movement of Ornithodoros turicata (Acari: Argasidae) in gopher tortoise burrows. Journal of Medical Entomology, 26(4), 279–283. https://doi.org/10.1093/jmedent/26.4.279
Balasubramanian S, Grunwald AP, Busselman RE, Olson MF, Davila E, Briggs C, Eldridge DS, Higgins B, Bass B, Cropper TL, Casey TM, Edwards T, Teel PD, Hamer SA, Hamer GL. (2024). Blood meal metabarcoding of the argasid tick (Ornithodoros turicata Dugès) reveals extensive vector-host associations. Environmental DNA, 6(1), e522. https://doi.org/10.1002/edn3.522
Beck AF, Holscher KH, Butler JF. (1986). Life cycle of Ornithodoros turicata americanus (Acari: Argasidae) in the laboratory. Journal of Medical Entomology, 23(3), 313–319. https://doi.org/10.1093/jmedent/23.3.313
Botero-Cañola S, Torhorst C, Canino N, Beati L, O'Hara KC, James AM, Wisely SM. (2024). Integrating systematic surveys with historical data to model the distribution of Ornithodoros turicata americanus, a vector of epidemiological concern in North America. Ecology and evolution, 14(11), e70547. https://doi.org/10.1002/ece3.70547
Bourret TJ, Boyle WK, Zalud AK, Valenzuela JG, Oliveira F, Lopez, J. E. (2019). The relapsing fever spirochete Borrelia turicatae persists in the highly oxidative environment of its soft-bodied tick vector. Cellular microbiology, 21(2), e12987. https://doi.org/10.1111/cmi.12987
Brown VR, Bevins SN. 2018. A review of African swine fever and the potential for introduction into the United States and the possibility of subsequent establishment in feral swine and native ticks. Frontiers in Veterinary Science 5: 11. https://doi.org/10.3389/fvets.2018.00011
Busselman RE, Olson MF, Martinez V, Davila E, Briggs C, Eldridge DS, Higgins B, Bass B, Cropper TL, Casey, TM, Edwards T, Teel PD, Hamer SA, Hamer GL. (2021). Host bloodmeal identification in cave-dwelling Ornithodoros turicata Dugès (Ixodida: Argasidae), Texas, USA. Frontiers in veterinary science, 8, 639400. https://doi.org/10.3389/fvets.2021.639400
Canino N, Torhorst C, Botero-Cañola S, Beati L, O'Hara KC, James A, Wisely SM. (2025). Development of a rapid and reliable surveillance method for Ornithodoros turicata americanus in gopher tortoise (Gopherus polyphemus) burrows in the southeastern United States. Medical and veterinary entomology, 39(1), 122–133. https://doi.org/10.1111/mve.12764
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